Many years ago I heard a speaker with a leopard print vest say that they only date someone once they have been friends for a year, and then if after 4 months they can't see it going any further, they end the relationship. Point being that you should know whether this person is compatible for you after only four months!
Another friend of mine said it should be three years, and a dear aunt of mine says you need to be sure you've seen them in every season.
As for me, I go with my gut. I mean, it's amazing how I can just
know after only two minutes with some guys that it will never work! And some guys, it takes about 10 minutes. Either way, am I too focused on figuring out why it will not work?
The problem here, and with everyone, is that we are just really much too inexperienced with the feeling that it
will work. It's the sort of thing that only really happens once for most people, if at all, and more than once for those who are truly lucky (if they are unfortunate enough to have had the first one not work or last for whatever reason).
I am becoming more convinced that knowing it will work is only a matter of choice. Love is a choice. We eventually, by figuring out what we like, what we don't like, meet someone who is tolerable and even fun to be with, and give it a shot.
Some say that it is a matter of the heart, not a choice, but I disagree. Our hearts are prejudiced with the decisions and values we have chosen over the years. When we meet someone that violates and offends these values (like those who chew with their mouths open or picks their nose in public), we do not love them. Or at least not enough to wish to have a relationship with them.
On the other hand, when we meet someone who shares these values, or does not offend our prejudice, we can choose to love them forever. And I believe you can find out these basics, like the chewing thing, within four months, so go for it!